Alzheimer's Alarm over Anaesthetics

Animal studies and test tube experiments are beginning to show that certain anaesthetics reduce the rate at which brain cells are born and develop, a factor that seems to be important to normal memory function. They may also directly affect the rate at which beta amyloid proteins bind together. This could be worrying, as the formation of clumps or "plaques" of these proteins is characteristic of Alzheimer's disease and may contribute to brain cell death.

Pravat Mandal of the University of Pittsburgh Medical School in Pennsylvania revealed that the inhaled anaesthetics halothane and isoflurane encourage clumping of beta amyloid protein, as does the commonly used intravenous anaesthetic propofol, at least at higher concentrations.

The findings back up a previous study in which Mandal used Nuclear Magnetic Resonance spectroscopy to show that halothane interacts directly with a pocket in the beta amyloid protein, changing its shape and encouraging neighbouring proteins to bind. Just 6 hours of exposure to halothane is sufficient to trigger protein clumping similar to that seen in people with Alzheimer's, he says.

Although halothane is rarely used in North America or Europe, it is commonly used in Asia and Africa because it is very cheap. "It is a seriously deadly combination when an older person receives halothane," says Mandal, because as we get older we all have more beta amyloid in our brains. The other anaesthetics studied are more widely used in the US and Europe, often in combination, though these seem to take longer to exert their potentially deadly effects. The good news is that the intravenous anaesthetic thiopental appears to have no effect on the proteins.